Food shortages, malnutrition and migration will undo decades of development unless more funding is made available, the authors added.
Failure to act could jeopardise UN global development goals, they warn.
The findings were compiled by the Montpellier Panel, a group of experts from Europe and Africa.
The report - The Farms of Change: African Smallholders Responding to an Uncertain Climate Future - recommended that international donors and governments took action in a range of priority areas.
The concerns voiced by Sir Gordon, who is also director of Agriculture for Impact, echoed the findings of a report last year that warned that many small-scale farmers across the continent faced the threat of "failed seasons".
The 2014 publication called for the adoption of "climate-smart agriculture" that will help make crops more resilient to future extreme weather events.
Another report published last year, On Trial: GM Crops in Africa, produced by UK think-tank Chatham House, said: "Increasing agricultural productivity and adapting farming to climate change are central to Africa`s development prospects."
It suggested that sub-Saharan Africa`s agricultural sector would benefit if it was able to harvest the fruits of biotechnology in order to establish sustainable development.
But it also said that a key challenge was being able to attract the necessary funding for biotechnology projects that focused on staple crops, such as cassava, as such food crops had a limited market globally.
Figures estimate that 200 million Africans are chronically malnourished and five million people each year die as a result of hunger.
The Montpellier Panel report that without urgently needed investment to climate-proof Africa`s agriculture, the situation would become even more bleak.
It warned that by the middle of this century, hunger and child malnutrition could increase by more than 20% as a result of changes to the climate, undoing the gains made by the UN Millennium Development Goals.
However, Africa director of the International Food Policy Research Institute, Dr Ousmane Badiane, outlined why the report was calling for greater funding to climate-proof the continent`s farms.
He said: "When given the right options and incentives, farmers can drive sustainable agricultural development that builds resilience to disasters and greenhouse gas emissions."
Africa`s farmers `need urgent climate-proof investment`
25 September 2015
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A lack of investment will derail efforts to ensure Africa`s farmers can feed future generations in the face of climate change, a report has warned.
